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Mind-Blowing Fossil Preserves Tiny Horse Carrying Unborn Foal

BERLIN: The former oil shale mining site of Messel, near Frankfurt, Germany, is well known for its spectacular fossils of organisms that lived between 47 million and 48 million years ago, during the Eocene epoch.

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BERLIN: The former oil shale mining site of Messel, near Frankfurt, Germany, is well known for its spectacular fossils of organisms that lived between 47 million and 48 million years ago, during the Eocene epoch. But a fossil of the early horse species Eurohippus messelensis, described at this year’s Society of Vertebrate Paleontology meeting in Berlin, stands out even in that illustrious company.

The tiny specimen—full grown, Eurohippus was about the size of a modern fox terrier--preserves a mare and her unborn foal (circled in the image above) in exquisite detail, with many of the bones in anatomical position. Also visible are parts of the uterus, including the placenta and the so-called broad ligament that attaches the uterus to the mare’s lumbar vertebrae and helps support the fetus. The soft tissue is not preserved directly, but as images formed by the petrification of bacteria that replaced the soft tissue when the animals died.

Comparing the fossil to the known phases of fetal development and birth in modern horses, Jens Lorenz Franzen of the Senckenberg Research Institute and his colleagues determined that the mare did not die during birth. The fetus was nearly at term when the pair died, but it was still facing upside down rather than having rotated into the right side up birth position.


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The exact cause of death of the mare and foal is unknown. But like many of the animals at Messel, they may well have perished from asphyxiation when ancient Lake Messel belched up a cloud of noxious carbon dioxide gas, as it did from time to time as a result of volcanic activity.

 

Kate Wong is an award-winning science writer and senior editor at Scientific American focused on evolution, ecology, anthropology, archaeology, paleontology and animal behavior. She is fascinated by human origins, which she has covered for more than 25 years. Recently she has become obsessed with birds. Her reporting has taken her to caves in France and Croatia that Neandertals once called home, to the shores of Kenya's Lake Turkana in search of the oldest stone tools in the world, to Madagascar on an expedition to unearth ancient mammals and dinosaurs, to the icy waters of Antarctica, where humpback whales feast on krill, and on a "Big Day" race around the state of Connecticut to find as many bird species as possible in 24 hours. Kate is co-author, with Donald Johanson, of Lucy's Legacy: The Quest for Human Origins. She holds a bachelor of science degree in biological anthropology and zoology from the University of Michigan. Follow Wong on X (formerly Twitter) @katewong

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